Her face launched her movie career when she was cast alongside Brad Pitt and Orlando Bloom in Troy, but Diane Kruger doesn’t want to be typecast. She reveals why Helen Mirren is her greatest inspiration, and how Jamie Oliver helps her to unwind

Another glorious spring morning in Los Angeles and the most beautiful woman in the world is dressed for the weather in a mocha and pink silk Miu Miu sundress, with slouchy brown suede boots. Diane Kruger winces at the ‘most beautiful’ soubriquet, but admits that since she was plucked from obscurity and cast as Helen of Troy – beating off competition from 3,000 actresses including, allegedly, Jennifer Aniston and Julia Roberts – in 2004, her movie career that has been nothing short of meteoric.

‘When I made Troy, it was only my second ever film, and it was an incredible opportunity, but it’s also been a very heavy weight to carry around with me,’ she says. ‘Even now it’s difficult to get work that interests me because you get pigeonholed very easily in Hollywood, and so I get offered a lot of parts where I’m just supposed to be the eye candy love interest. But I don’t want to complain – “Oh they always see me as a princess, poor little me” – because I would sound like such an idiot!’

Troy was regarded as a cinematic turkey – even the presence of Brad Pitt as Achilles and Orlando Bloom as Paris couldn’t save it – so it’s a testament to Diane’s on-screen presence that despite this, and the fact that her two-dimensional role made it hard to tell whether she could act or not, her stock nevertheless soared in the wake of the film’s release.

Her next major outings were the exhilarating blockbuster National Treasure and its sequel National Treasure 2: Book of Secrets, which grossed a spectacular $800 million (£400 million) worldwide, in which Diane appeared opposite Nicolas Cage.

‘I personally like the second movie better because it felt we all knew what we were doing and we had a blast,’ says Diane. ‘Nick was so unpredictable, it kept us all on our toes. Every day he would come on to the set and we would have no idea what to expect; he would suddenly do these crazy improvisations that would work so well they would end up in the movie.’

German-born Diane, 31, who speaks English without a trace of an accent, has matured into an even more beautiful woman than she was in her 20s. With a cascade of blond hair, porcelain skin and lapis lazuli eyes, the former model has the sort of effortlessly slim figure that would make the average A-lister, starving herself on miracle juice and edamame beans, weep into her green tea.

Diane with boyfriend Joshua Jackson

A respected name in European cinema, she opened the Cannes Film Festival last year, and considers Paris, rather than Hollywood, to be her home, yet is often filming in the US for months at a time. All the same, she has resisted falling prey to the body-conscious excesses of La-La land.

‘I haven’t caught the Californian bug of jogging with a personal trainer before a breakfast of wheatgrass,’ she laughs. ‘I like to keep fit by walking everywhere, which everyone finds shocking because no one goes anywhere on foot in this city – so when I say, “Hey, come on, it’s only five blocks,” I’m greeted with wide-eyed horror.’

Her boyfriend, former Dawson’s Creek star turned grown-up heart-throb Joshua Jackson, 29, is fortunately not averse to leaving the comfort of his air-con. ‘Joshua is very outdoorsy, and when I’m in Hollywood I live outside the city in the hills, so we go hiking together.’

The couple have been an item for two years, and despite rumours that Diane was recently displaying a telltale bump, she denies her thoughts are turning to matters maternal.

‘I don’t have any plans for a family yet. We’re both a little too young for that, but I can imagine that if I have children in the future I’ll completely immerse myself in motherhood, because I tend to get obsessive about whatever I’m doing at any particular point, whether it’s renovating a house, which I did for two years, stripping paint and sanding for days on end, or reading up for a new part, which can absorb me for months.’

Diane was previously married, for five years, to French actor-director Guillaume Canet (who is best known here for his starring role in The Beach, and is now dating Oscar-winner Marion Cotillard). The relationship apparently foundered because their careers took them in different directions, literally, and they didn’t spend enough time together.

She is unwilling to talk about the marriage, simply saying it was ‘a different time in my life’. But she concedes that she and Jackson work hard to see each other as often as they can: ‘I’ve realised that if you want to make it happen enough, it will happen.’

Although independent in spirit and single-minded in her pursuit of her goals, Diane also possesses rather a contradictory ‘que sera sera’ fatalism about her life and career. ‘I firmly believe that when one door closes another door opens. If I never got another acting job again, I would turn to writing or production – I’ve already co-produced an independent film in France. There’s always something new to try and I find that exciting rather than scary.’

Diane was born in the rural backwater of Algermissen, a village near Hanover, and her parents divorced when she was a young girl. Diane, who has a younger brother, Stefan, studied ballet and hoped to become a professional dancer, but at the age of 13 she suffered an injury to her right knee joint, and needed to have two metal plates inserted (it still troubles her in damp weather or after skiing).

At that point she decided she would never make the grade to her own satisfaction and become a prima ballerina, so she gave up dance overnight, a reflection of her drive and ambition, even as a child. Fate intervened in spectacular fashion when, two years later, she won an Elite modelling competition and left Germany for the ateliers of Paris.

‘Looking back, I can hardly believe my mother let me go off aged 15, and I’m not sure I’d let a daughter of mine go abroad on her own at that age, but I was a good girl and the fact that my mother placed her trust in me made me grow up quite quickly, because I wanted to justify that trust.’

At first it was all very bewildering. Unable to speak French, Diane was nonetheless given a Metro map and dispatched to castings, where she struggled to understand what was going on. But she soon became very much in demand internationally and, as a result, she knows many of the leading designers personally including Karl Lagerfeld who is a close friend: ‘Karl lives near me in St-Germain, so when I am going to a premiere and I need to borrow a dress, I just call him up.’

Having worked with the best in the business, she has acquired both an appreciation of and passion for high-end fashion. ‘I adore Chanel, Valentino and Ferretti and I also really like Phillip Lim in the US. I’ve always been drawn to classic shapes and styles rather than anything too modern and I avoid fashion that changes every season.

‘I look at someone like Victoria Beckham and, although I would never choose the outfits she wears, I admire her for always appearing in the latest cutting-edge look; that takes a lot of thought and planning. I just don’t have the time or the patience. I’m very lucky to get sent a lot of clothes, but I don’t have a stylist organising my wardrobe.’

Fluent in French and English as well as German, Diane is justifiably proud of her modelling days, and cavils at the idea that she might be classed as just another wannabe Maw (model/actress/whatever). Far from wandering off the catwalk one day and on to a movie set, after deciding she wanted to go into acting, she did it properly and at the age of 22 enrolled in the Cours Florent drama school in Paris, which counts Isabelle Adjani, Daniel Auteuil and Casino Royale actress Eva Green among its alumni.

The age of 30 is usually the point when leading ladies start to fret about younger, prettier starlets overtaking them. Diane, however, seems genuinely unconcerned. ‘Of course I look in the mirror and I only see the imperfections and the blemishes; then again so do all women. But I don’t worry about how it will affect my career. Maybe when I’m 50 or 60 I’ll feel inclined to have a nip or a tuck. I can’t speak for other actresses, but my life doesn’t revolve round how I look.

'I see my future in European cinema, because over there I can have a career for much longer than in Hollywood; actresses such as Catherine Deneuve and Emma Thompson still have interesting stories to tell, and aren’t automatically cast in the “mum” role.’

As far as ageing gracefully goes, Diane looks to the British icon and Oscar-winner Helen Mirren, who appeared alongside her in National Treasure 2: Book of Secrets. Meeting and working with Mirren, now 62, proved something of a revelation.

‘Helen is amazingly beautiful, very sexy and has a wonderful self-assurance that I aspire to,’ says Diane. ‘She makes brilliant movies on her own terms and always seems so fresh and fun to be around, it’s very inspirational.’

At present, Diane is filming a movie called Out of Breath with Dermot Mulroney (of The Wedding Date fame) and Oscar-winner Forest Whitaker, which tackles the uncomfortable subject of the trade in human organs. Diane plays a mother whose daughter urgently needs a lung transplant. After languishing on a transplant list, without finding a donor, the girl becomes so ill that Diane’s husband (Mulroney) decides the only way to save her life is to search out a ring of unscrupulous criminals dealing in organs.

'Parties aren't that much fun in LA because no one drinks; they drive everywhere. If I really want to party I go to New York'

‘It’s a hugely powerful script and the whole movie is quite intense,’ says Diane. ‘I love my part – it’s challenging and I really like that.’

So, what does Diane do to unwind after those intense days on set? ‘I’ll stay home and cook – often it’s lasagne for some friends. I’ve recently discovered Jamie Oliver; his book Jamie’s Italy is fabulous and the recipes really work. I can even make pasta from scratch!’

Not that it’s all nights in by the stove for one of Hollywood’s most invited couples, and Diane admits she loves getting dressed up for parties – though also confides that this is usually the highlight of an evening in Tinseltown.

‘Parties aren’t all that much fun in LA because no one drinks; they drive everywhere. It’s all about seeing and being seen, rather than having a great time. I love to dance, so if I really want to party I go to New York, where it’s a very different scene. But I’ll always love dressing up. When I’m wearing a fabulous gown and walking down a red carpet with my boyfriend, that’s when I feel beautiful.’

National Treasure 2: Book of Secrets will be out on DVD and Blu-ray disc on 2 June